Figures

In-plane area expansion lowers the free energy of a channel-membrane system under tension.

Analog of a membrane under tension showing tethered weights in a gravitational field pulling the membrane taut, adapted from Ursell et al. (2008). (a) When the channel is closed, potential energy from the weights is high. (b) When the channel opens and in-plane area expands, the weights are lowered, and the potential energy of the system is decreased.

CryoEM reconstruction of mPiezo1.

(a and b) Representative 2D averaged classes, viewed from the top (a), and the side (b), scale bar 10 nm. (c and d) Atomic model of the trimeric channel shown as ribbon diagram, viewed from the top (c), and the side (d). The three subunits are colored in red, green and blue, respectively. (e) Fourier shell correlation (FSC) curves calculated between two half maps after C1 masked refinement and post-processing in RELION. (f) Local resolution of density map from C1 masked refinement, estimated by Blocres. The map shown is low-pass filtered to 3.8 Å and sharpened with a b-factor of −200 Å2.

Topology of mPiezo1.

(a) Cartoon representation of a monomer, rainbow-colored with C-terminus in red and N-terminus in blue, except for the first 12 TMs that are not visible in our structure. Helices within a single 4-TM unit are colored uniquely. Helices are shown as cylinders, loops as solid lines, and unresolved regions as dotted lines. C-terminal extracellular domain (CED) is simplified as a box. A ribbon diagram of 4-TM unit 6, consisting of TM 21 to 24, is shown in the left inset panel with N- and C- termini labeled. The right inset panel shows a ribbon diagram of the pore region, formed by TM37, TM38 and the PE helix from all three subunits. (b) A ribbon diagram of a monomer rainbow-colored as in A, viewed from top. Each 4-TM unit is highlighted in a red box with TM number labeled.

mPiezo1 trimer in curved micelle.

(a) The same ribbon diagram of a monomer taken from the trimer, as in 3B, viewed from the side, with N- and C- termini labeled. Approximate locations of planar membrane interfaces are shown as grey lines. (b) Ribbon diagrams of a trimer in an unsharpened map, contoured at 6σ, showing micelle density. Top, side and bottom views are shown. (c) Surface representation of a trimer, colored based on electrostatic potentials in aqueous solution containing 150 mM NaCl, calculated using APBS, with positive shown blue, neutral white, and negative red. Top, side and bottom views are shown.

Interface between CED and TM loops.

(a) Ribbon diagram of a trimer in an unsharpened map. One of the three contact regions between CED and TM loops is highlighted in a black box. (b) Zoomed-in view of the region in black box in (a) as surface representation, colored based on electrostatic potentials in aqueous solution containing 150 mM NaCl, calculated using APBS, with positive in blue, neutral in white, and negative in red. (c) Ribbon diagram of the helices in contact, colored as in Figure 3. Interacting residues are shown as sticks.

Pore of the mPiezo1 channel.

(a) Ion-conduction path viewed from the side. The distance from the pore axis to the protein surface is shown as grey sphere. Cα trace of the pore (TM37, TM38, hairpin and PE helices) is shown in yellow. Residues facing the pore are shown as sticks. Constricting residues are labeled. (b) Radius of the pore. The van der Waals radius is plotted against the distance from the top along the pore axis. Constricting residues are labeled as in A. (c) Stereo view of the side-chain density around constricting residues. The map is contoured at 6σ and sharpened with a b-factor of −200 Å2. The atomic model is shown as sticks, colored according to atom type: yellow, carbon; red, oxygen; blue, nitrogen; and orange, sulfur.

Pore region of the mPiezo1 channel.

(a) Potential ion-conduction path including the CED viewed from the side. The distance from the pore axis to the protein surface is shown as grey sphere. Cα trace of the pore region (residues 2116 to 2546) is shown in yellow. Estimated membrane interfaces on the basis of protein surface features are shown as grey lines. Four vestibules are labeled as in P2X and ASIC channels. Position of one of the fenestrations is indicated with an asterisk. (b) Radius of the potential ion-conduction pathway including the CED. The van der Waals radius is plotted against the distance from the bottom along the pore axis. (c) Ribbon diagram of the pore region in grey, with the elbow and triangular base helices highlighted in yellow. Both side view and bottom view are shown. (d) Ribbon diagram of the pore region in grey, with the hairpin and PE helices highlighted in red. Both side view and bottom view are shown.

Model of tension-gating in mPiezo1.

(a) Cα trace representation of a trimer placed in a semi-sphere-shaped membrane 3.6 nm thick, idealized from the curved micelle density. The mid-plane semi-sphere has radius of 10.2 nm and is centered 4.0 nm above the projection plane. The three subunits are shown in red, green and blue, respectively. (b) Ribbon diagram of a trimer in the idealized membrane. The ‘beam’ formed by residues 1300–1365 is highlighted in red, the cross-helices are highlighted in yellow, while the remaining protein is colored in grey. (c) Illustration of projection area (circle in top plane) changing as the surface curvature of the channel and local membrane (bottom plane) changes. (d) Theoretical activation curves corresponding (ΔGprot + ΔGbend)=20 kBT (red) or 40 kBT (blue) and ΔAproj = 20 nm2 or 60 nm2. The curves are generated through Po = (1 + Exp[(ΔGprot + ΔGbend) - γΔAproj])−1.

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